As a form of a scanning probe microscope, there is a non-contact atomic force microscope (a microscope that can measure the field of force from a specimen without touching the surface of the specimen). In the vicinity of the surface of the specimen where a short-range force such as an atomic force is predominant, it is difficult for a conventional non-contact atomic force microscope to measure a long-range force such as a magnetic force. In order to measure the long-range force, it is necessary to move the probe of the microscope away from the specimen such a distance that the long-range force is predominant. However, moving the probe away from the specimen disadvantageously causes a spatial resolution to significantly degrade as compared with an atomic resolution.
On the other hand, in recent years, manufactures have fiercely competed with one another in technology for increasing the density and capacity of a magnetic recording medium that is a main component of a high-density magnetic storage device, and thus the density of the magnetic recording medium is exponentially increased. In the research and development of the magnetic recording medium described above, it is essential to use a method of observing the minute magnetic domain structure of the magnetic recording medium, and a non-contact atomic force microscope (magnetic force microscope (MFM)) that can measure a magnetic force is used. An example of the device that can be used as the magnetic force microscope (MFM) is disclosed in Patent Literature 1.